High-resolution distortion-free diffusion imaging using hybrid spin-warp and echo-planar PSF-encoding approach
High-resolution distortion-free diffusion imaging using hybrid spin-warp and echo-planar PSF-encoding approach
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DOI：
10.1016/j.neuroimage.2017.01.008
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发表时间：
2017-03-01
期刊：
影响因子：
5.7
通讯作者：
Speck, Oliver
中科院分区：
文献类型：
--
作者：
In, Myung-Ho;Posnansky, Oleg;Speck, Oliver
高分辨率扩散加权成像（DWI）在提供有关体内组织微观结构的独特信息方面具有巨大潜力。尽管单次回波平面成像 (EPI) 是最流行的 DWI 工具，但由于 T2* 模糊以及磁化率和涡流引起的几何畸变，尤其是在 7T 等超高场 (UHF) 下，其在高分辨率 DWI 中的应用受到限制。在这项研究中，我们采用了受点扩散函数（PSF）映射启发的混合自旋扭曲和回波平面编码策略，并针对高分辨率和无失真扩散成像应用对其进行了优化。更具体地说，将 2D 导航器回波添加到原始序列中，以进行逐个镜头运动引起的相位误差估计和校正。空间编码在 PSF 和 EPI 相位编码维度之间共享，允许短回波序列在 UHF 下有效地保留扩散和导航信号，其中 T2 衰减相对较快。此外，在PSF维度中应用可变k空间间距，并与EPI-PE维度中的并行成像相结合，进一步加速PSF采集。结果表明，该方法可以在 7T 下产生各向同性亚毫米分辨率，而不会出现 T2* 模糊和几何畸变，并且能够利用扩散对比度清晰详细地描绘体内人脑结构。此外，还介绍了所提出的 3 T 高分辨率扩散成像方法的结果。
High-resolution diffusion-weighted imaging (DWI) has great potential to provide unique information about tissue microstructure in-vivo. Although single-shot echo-planar imaging (EPI) is a most popular tool for DWI, its application for high-resolution DWI is limited due to T2* blurring and susceptibility-and eddy-current induced geometric distortions, especially at ultra-high field (UHF) such as 7T. In this study, we adapt a hybrid spin-warp and echo-planar encoding strategy inspired by point spread function (PSF) mapping and optimize it for high-resolution and distortion-free diffusion imaging applications. More specifically, a 2D navigator echo is added into the original sequence for shot-to-shot motion-induced phase error estimation and correction. The spatial encoding is shared between the PSF and the EPI phase encoding dimension allowing short echo trains to preserve the diffusion and navigator signals efficiently at UHF, where T2 decay is relatively fast. In addition, variable k-space spacing was applied in the PSF dimension and combined with parallel imaging in the EPI-PE dimension to further accelerate the PSF acquisition. The results demonstrate that this method can yield isotropic submillimeter resolution without T2* blurring and geometric distortions at 7T and enables a clear and detailed delineation of human brain structures in-vivo with the diffusion contrasts. In addition, results of the proposed approach for high-resolution diffusion imaging at 3 T are presented.